Training sandal and method of use

ABSTRACT

A training sandal for barefoot running conditioning is provided. According to the method of the present invention two sandals are provided, each sandal having an elastic sole that decreases in elasticity with use in running and walking. A wearer then runs with the sandals to cause the elastic sole to decrease in elasticity, whereby the feet of the wearer are gradually strengthened to accommodate bare foot running.

CONTINUATION-IN-PART

This U.S. nonprovisional patent application is a Continuation-in-Part of U.S. Provisional Patent Application 61/389,820 filed on Oct. 5, 2010 by inventor Lester Waddel, the same inventor of this U.S. nonprovisional patent application, and titled TRAINING SANDAL AND METHOD OF USE. This U.S. nonprovisional patent application claims benefit of the priority date of U.S. Provisional Patent Application 61/389,820 for all purposes, and incorporates the entire disclosure of U.S. Provisional Patent Application 61/389,820 into this U.S. nonprovisional patent application.

FIELD OF THE INVENTION

The present invention is directed toward human footwear and more particularly toward sandal-style footwear that is adapted for use in striding, running and jogging.

BACKGROUND OF THE INVENTION

Among sports medicine practitioners, the traditional model of a healthy human gait cycle that begins with a heel strike on the ground is being challenged by an alternate model wherein the forefoot strikes the ground before the heel. In the more traditionally taught heel-first model of healthy running and walking, the gait cycle begins with a heel strike phase that is followed by a flat foot phase and a succeeding toe off phase. The heel strike phase lasts until the front bottom of the foot or shoe contacts the ground in the flat foot phase. The runner's weight rolls forward and inward onto the forefoot as the arch of the foot collapses in the flat foot phase. The runner's weight is then supported by the inner and front part of the forefoot wherefrom the foot is pushed off the ground and propelled forward. The flat foot phase lasts until the runner's heel lifts, thereby beginning the toe off phase.

In the heel strike and the flat foot phases of the heel-first gait model, the runner's foot typically pronates or supinates, and such pronation or supination will result in lateral movement of the runner's foot, ankle and lower leg. Conventional running shoes attempt to stabilize the runner's foot by providing a foot-encompassing supportive upper and a generally rigid heel cup and cushioning sole shaped to snugly receive, cushion and control the runner's heel. This heel-first style shoes typically isolate and bind the wearer's feet and limit dissipation of force within the foot.

The newer, alternative healthy forefoot-first gait model teaches that the ball or forefoot of the runner should strike the ground first and before the heel of the same foot, wherein it is empirically proven that the foot structure may accept, absorb and dissipate the force of the foot strike in a more healthy and diffuse way within the whole foot. The heel then follows the forefoot in striking the ground in this newer, forefoot-first gait model. Certain advocates of the forefoot-lead gait model even advise runners to run barefoot on hard surfaces, such as hard packed earth. Yet most modern humans in developed countries have spent most of their lives striking the ground first with the underside of their heels. A transition from a heel-first gait that relies upon a heavily cushioned shoe to a barefooted forefoot-lead strike can be difficult and medically challenging to anyone who has spent years in prior art, heel isolating footwear.

In another aspect of prior art footwear, shoes are generally designed to support and maintain the existing structure of a human foot in a same manner during the useful life of the footwear. In particular, running shoes are designed and manufactured to maintain a consistent degree of cushioning of the underside of foot heel. Degradation of heel cushioning is considered to be undesirable for good foot health, and the wearer is advised to discard a pair of shoes when the cushioning quality of the shoe is significantly reduced. Yet a reduction of a cushioning quality of a shoe over time can be useful in encouraging a foot to gradually adapt from the heel-strike gait and to strengthen the foot to effect the forefoot-first gait.

It would, therefore be desirable to provide footwear for running and other activities that can provide support and cushioning to dissipate the impact forces of a forefoot-first striking gait and to aid a wearer to transition from a heel-strike gait to a forefoot-first gait.

SUMMARY OF THE INVENTION

Towards these objects and other objects that are made obvious in light of the present invention, a training sandal is provided. In one aspect of the invention a barefoot running training sandal allows a wearer's foot to move the muscle, ligament, and joints naturally. The invented sandal may include a sole, a forefoot strap and an ankle strap assembly. The sole may include an elastic material that compresses, breaks down and/or becomes more dense and less elastic and less resilient with use and provides less cushioning of the wearer's foot over the useful life of the sandal.

Certain alternate preferred embodiments of the present invention include a sole that is narrowed in thickness in a front area of the invented sole at least partially narrows, or thins, along an axis leading from the forefoot and toward the tip of the toes of a wearer's foot.

According to the method of the present invention, a pair of sandals may be shaped for a left and a right foot respectively, and provided to a wearer. Each sandal of the shaped pair would have an elastic sole that decreases in elasticity and/or resilience with use in walking and running, and optionally decreasing in thickness while increasing in density with use in running and walking. The wearer then runs and/or walks while wearing an invented shaped sandal coupled to each foot to cause the elastic sole to gradually decrease in elasticity and/or resilience, whereby the feet and body of the wearer are gradually conditioned to accommodate bare foot running and walking with a reduced incidence of injury.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference in their entirety and for all purposes to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.

Such incorporations include the following U.S. patents, the disclosures of which are incorporated in their entirety into this application and for all purposes: (1.) U.S. Pat. No. 7,103,993, inventor Sakai; (2.) US Patent Application Publication No. 20080155856, inventor Bathum; (3.) U.S. Pat. No. 7,320,188, inventor Bathum; (4.) U.S. Pat. No. 4,967,750 Cherniak; (5.) U.S. Pat. No. 4,793,075, inventor Thatcher; (6.) U.S. Design Pat. No. D458,009, inventor Ritter, et al.; (7.) U.S. Pat. No. 4,869,000, inventor York, Jr.; (8.) US Patent Application Publication No. 20090064542, inventor Figueroa; (9.) U.S. Pat. No. 5,787,608, inventor Greenawalt; (10.) U.S. Design Pat. No. D543,686, inventor Anderson, et al.; (11.) U.S. Pat. No. 1,964,705, inventor Pellkofer; and (12.) U.S. Pat. No. 6,543,157, inventor Pan.

The publications discussed or mentioned herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Furthermore, the dates of publication provided herein may differ from the actual publication dates which may need to be independently confirmed.

BRIEF DESCRIPTION OF THE DRAWINGS

These, and further features of the invention, may be better understood with reference to the accompanying specification and drawings depicting preferred configurations, in which:

FIG. 1 is a perspective view of a preferred embodiment of the invented sandal;

FIG. 2 is an exploded front view of the invented sandal of FIG. 1;

FIG. 3 is a side view of the invented sandal of FIGS. 1 and 2;

FIG. 4 is a top view of the invented sandal of FIGS. 1 through 3;

FIG. 5 is an exploded perspective view of the invented sandal of FIGS. 1 through 4; and

FIG. 6 is a side view of an alternate preferred embodiment of the present invention, wherein a sole of the alternate preferred embodiment is tapered in a toe region of the sandal to present a thinner region of material below a wearer's toes.

DETAILED DESCRIPTION

In describing aspects of the invention, certain terminology will be utilized for the sake of clarity. Such terminology is intended to encompass the recited example, as well as all technical equivalents, which operate in a similar manner for a similar purpose to achieve a similar result.

It is to be understood that this invention is not limited to particular aspects of the present invention described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

Methods recited herein may be carried out in any order of the recited events which is logically possible, as well as the recited order of events.

Where a range of values is provided herein, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, the methods and materials are now described.

It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation.

The foregoing disclosures and statements are illustrative only of the Present Invention, and are not intended to limit or define the scope of the Present Invention.

Referring now to FIG. 1, FIG. 1 is a perspective view of a preferred embodiment of the invented sandal 2, or first sandal 2. The first sandal 2 extends In length laterally along an X-axis (as per FIG. 3 and FIG. 4) that traverses through a heel point X1 and a toe point X2 and includes a sole 4, a forefoot strap 6 and an ankle strap assembly 8. The forefoot strap 6 is adapted to removably couple the wearer's foot (not shown) to the sole 4. The ankle strap assembly 8 is adapted to detachably couple the wearer's ankle (not shown) to the sole 4.

A heel area H of the sole 4 extends along an x-axis for three inches starting at the heel point X1 and towards the toe point X2 along the X-axis. A toe area T of the sole 4 extends for three inches starting at the toe point X2 and extending towards the heel point X1 along the X-axis.

The sole 4 is selected from suitable materials known in the art that degrade in elasticity and/or resilience and cushioning support of the feet of the wearer as the sandal 2 is worn by a human wearer in running and/or optionally in walking, whereby the wearer's foot (not shown) is gradually conditioned to better accommodate to barefoot running and the forefoot-first running gait and styles.

Referring now generally to the Figures and particularly to FIGS. 2, and 5, the sole 4 presents an outer sole 4.A positioned for contact with the ground (not shown) and a mid-sole 4.B disposed between the outer sole 4.A and a top sole 4.C. The outer sole 4.A is made of material selected for durable contact with the ground, and may comprise or be a VIBRAM ROCK CLIMBING SOLE™ outer sole material as marketing by Vibram, Inc. of Concord, Mass., or other suitable material known in the art. The outer sole 4.A presents a thickness along a Y-axis preferably within the range of 0.25 inch to 0.0625 inch, or alternatively presents a thickness along the Y-axis of 1.8 millimeter and/or comprises rubber. It is understood that the Y-axis and the X-axis are mutually orthogonal.

The mid-sole 4.B is elastic and made of material intentionally selected for both an initial elasticity and for having a quality of losing elasticity over time with use in running and walking. Preferably, the sole 4, and/or the mid-sole 4.B alone, initially present a measure of hardness in the range of 30 to 40 hardness value within the D2240 type A durometer scale as maintained and published by ASTM International of West Conshohocken, Pa.

The mid-sole 4.B may be or comprise ethylene vinyl acetate (also known as “EVA”) or other suitable and similarly elastic and/or similarly resilient material known in the art. EVA is the copolymer of ethylene and vinyl acetate, wherein the weight percent vinyl acetate may vary in the range of from 10% to 40%, with the remainder being ethylene. Alternatively or additionally, the sole 4 may comprise material that decreases in elasticity preferably in the range of 50% to 200% of the loss of elasticity as exhibited by EVA at a same usage rate, at a similar environment, under similar conditions of use and/or under a same load and load profile.

Yet alternatively or additionally, the sole 4 may comprise material that decreases in resilience preferably in the range of 50% to 200% of the loss of resilience exhibited by EVA at a same usage rate, at a similar environment, under similar conditions of use and/or under a same load and load profile.

Still alternatively or additionally, the sole 4 may comprise material that decreases in cushioning of the wearer's foot preferably in the range of 50% to 200% of the loss of foot cushioning exhibited by EVA at a same usage rate, at a similar environment, under similar conditions of use and/or under a same load and load profile.

The thickness of the mid-sole 4.B, that is the dimension along the Y-axis, i.e., the dimension of the mid-sole 4.B that is disposed between the outer sole 4.A and the top sole 4.C, is preferably within the range of 0.125 inch to 1.0 inch, and more preferably within the range of 0.25 inch to 0.5 inch. The outer sole 4.A may be affixed to the mid-sole 4.0 with an adhesive, such as barge glue, or coupled with the mid-sole 4.0 with another suitable adhesive known in the art or by other suitable material or means known in the art. In addition, the mid-sole 4.B may further be affixed to the top sole 4.0 with an adhesive, such as barge glue, or coupled with the mid-sole 4.0 with another suitable adhesive known in the art or by other suitable material or means known in the art.

The top sole 4.0 is selected to present a foot surface 4.D, or top surface 4.D, for comfortable contact with a wearer's foot (not shown) and may comprise leather, cork, pigskin, or other suitable material known in the art. The top sole 4.0 may preferably generally present a thickness along the Y-axis preferably in the range of 0.25 inch to 0.0625 inch, and more preferably in the range of 0.050 inch to 0.070 inch.

In the first sandal 2, the top foot surface 4.D of the top sole 4.0 and a bottom surface 4.E of the outer sole 4.A (as shown in FIGS. 2, 3, and 5) each present separate flat surfaces that are co-planar with each other and within a planar parallelism deviation of less than 20 degrees. More preferably the top foot surface 4.D of the top sole 4.0 and the bottom surface 4.E of the outer sole 4.A each present a separate flat surface that are initially co-planar with each other within a planar parallelism deviation of less than 5 degrees.

Referring now generally to the Figures and particularly to FIGS. 1 and 5, the forefoot strap 6 may be or comprise a one-inch wide, tubular nylon webbing, wherein the width dimension of the forefoot strap 4 passes along the X-axis. The forefoot strap 6 is positioned to contact the forefoot of the wearer (not shown) and without restricting mobility of the wearer's toes (not shown). The forefoot strap 6 is attached both (a.) at a lateral strap length 6.A to a lateral side 4.F of the sole 4 at a lateral sole area 4.G; and (b.) at a medial strap length 6.B to a medial side 4.H of the sole 4 at a medial sole area 4.I. The forefoot strap 6 may be attached to the sole 4 by means of stitching and/or adhesion. Alternately or additionally, the lateral strap length 6.A and/or the medial strap length 6.B may extend through the top sole 4.0 and/or the midsole 4.B and be attached by adhesion or stitching within the sole 4.

Referring now generally to the Figures and particularly to FIGS. 1, 2 and 5, the ankle strap assembly 8 includes a two millimeter thick arch strap protector 8.A, a ladder lock 8.B, a one inch wide flat nylon webbing cinch strap 8.C, a one inch wide flat nylon webbing heel strap 8.D, a one inch wide flat nylon webbing lateral arch strap 8.E, a one inch tri-loop strap slide 8.F, and (as shown in FIG. 2) a one inch wide flat nylon webbing medial arch strap 8.G.

The arch strap protector 8.A preferably extends along the X-axis for a length in the range of from one inch to three inches and also preferably extends along the Y-axis for a length in the range from three inches to ten inches. The arch strap protector 8.A is preferably made of strong flexible sheet material, such as a neoprene (TM) synthetic rubber fabric made from polymers of chloroprene as marketed by DuPont Corporation of Dover, Del., or other suitable material known in the art. The arch strap protector 8.A is attached to the sole 4 at both a lateral strap length 8.A.1 and a medial strap length 8.A.2 by stitching and/or adhesion. The arch strap protector 8.A may be angled 20 degrees to 5 degrees less in front cross-section, i.e., a present a narrower cross-section toward the toe section T and along the X-axis, to match an angle and shape of the top of the wearer's foot (not shown).

The heel strap 8.D is attached by stitching or adhesion to the heel area H of the sole 4 at a heel end length 8.D.1 and is attached to, and/or wraps around the captures the cinch strap 7 at a looped end length 8.D.2. Alternately or additionally, the heel end length 8.D.1 may extend through the top sole 4.0 and/or the midsole 4.B and be attached by adhesion or stitching within the sole 4. The heel strap 8.D may be one inch wide along a Z-axis and be or comprise nylon webbing or other suitable strap material known in the art. It is understood that the Z-axis is orthogonal to both the X-axis and the Y-axis.

The lateral arch strap 8.E is attached by stitching or adhesion to the lateral sole side 4.F of the sole 4 at a sole end length 8.E.1. Alternately or additionally, the lateral arch strap sole end length 8.E.1 may extend through the top sole 4.0 and/or the midsole 4.B and be attached by adhesion or stitching within the sole 4. The lateral arch strap 8.E is additionally attached at a slide end length 8.E.2 to the tri-loop strap slide 8.F by adhesion to, or alternatively or additionally by stitching through, a triangular aperture 8.F.1 of the tri-loop strap slide 8.F. The lateral arch strap 8.E may be one inch wide along the X-axis and be or comprise nylon webbing or other suitable strap material known in the art.

The medial arch strap 8.G is attached by stitching or adhesion to the sole medial side 4.H of the sole 4 at a sole end length 8.G.1. Alternately or additionally, medial arch strap sole end length 8.G.1 may extend through the top sole 4.0 and/or the midsole 4.B and be attached by adhesion or stitching within the sole 4. The medial arch strap 8.G is further attached to the ladder lock 8.B at an adjustor end length 8.G.2 by weaving the adjustor end length 8.G.2 through at least two strap apertures 8.B.1-8.B.3 of the ladder lock 8.B. The lateral arch strap 8.E may be one inch wide along the Z-axis and be or comprise nylon webbing or other suitable strap material known in the art.

The cinch strap 8.0 is stitched and/or adhered to the ladder lock 8.B at a cinch-adjustor end 8.C.1 and traverses through the heel strap loop 8.D.2. The cinch strap 8.0 further extends through a loop aperture 8.F.2 of the tri-loop strap slide 8.F and is again coupled to the ladder lock 8.B at a cinch-adjustor length 8.C.2 by weaving the cinch-adjustor length 8.C.2 through at least two strap apertures 8.B.1-8.B.3 of the ladder lock 8.B.

Referring now to FIG. 3, FIG. 3 is a side view of the first sandal 2 as fully assembled. It is understood that the arch strap protector 8.A, the ladder lock 8.B, the cinch strap 8.C, the heel strap 8.D, the lateral arch strap 8.E, the tri-loop strap slide 8.F, the medial arch strap 8.G may be coupled or attached to the sole 4 and/or one or more ankle strap assembly elements 8.A-8.G by (a.) a suitable adhesive(s) known in the art; (b.) stitching; (c.) sewing; and/or (d.) other suitable alternate or additional coupling means or methods known in the art.

It is further understood that the forefoot strap 6 may be coupled or attached to the mid-sole 4 by (a.) a suitable adhesive(s) known in the art; (b.) stitching; (c.) sewing; and/or (d.) other suitable alternate or additional coupling means or methods known in the art.

Referring now to FIG. 4, FIG. 4 is a top view of the first sandal 2 as fully assembled. The cinch strap 8.0 is shown passing through the strap slide aperture 8.F.2 of the strap slide 8.F.

Referring now to FIG. 5, FIG. 5 is an exploded view of the first sandal 2. The cinch strap 8.0 is shown passing through both the strap slide aperture 8.F.2 and through one or more strap adjustor apertures 8.B.1-8.B.3 of the ladder lock 8.B.

FIG. 6 is a side view of an alternate preferred embodiment of the present invention 10 (hereinafter, “second sandal” 10), wherein an alternative second sole 12 of the alternate preferred embodiment is tapered in the toe area T of the second sandal 10 to present a thinner region of material below a wearer's toes (not shown). The toe area T extends for up to three inches starting at the toe point X2 and extending towards the heel point X1 along the X-axis. The second sole 12 presents a sole end thickness T1 along the Y-axis at the toe point X2 and a sole body thickness T2 along the Y-axis at a distance L from the toe point X2 of the second sole 12, where the distance L traverses from the toe point X2 and towards the heel point X1 and along the X-axis. The end thickness T1 is preferably within the range of from 0.01 inches to 0.2 inches, and is more preferably in the range from 0.0625 inches to 0.125 inches. The total and combined sole body thickness T2 of the second sole 12 is preferably within the range of from two inches to 0.25 inches, and is more preferably in the range from one inch to 0.5 inches.

According to the method of the present invention, a pair of first sandals 2 may be shaped for a left and a right foot respectively, and provided to a wearer. Each first sandal 2 of the shaped pair would have an elastic sole 4 that both increases in density and decreases in elasticity with wear. The wearer then runs, and optionally walks, with one shaped first sandal 2 coupled to each human foot to cause the elastic sole of the first sandal 2 to decrease in elasticity, whereby the feet of the wearer are gradually strengthened to accommodate bare foot running or walking.

The above description is intended to be illustrative, and not restrictive. Although the examples given include many specificities, they are intended as illustrative of only certain possible examples of the Present Invention. The examples given should only be interpreted as illustrations of some of the examples of the Present Invention, and the full scope of the Present Invention should be determined by the appended claims and their legal equivalents. Those skilled in the art will appreciate that various adaptations and modifications of the just-described examples can be configured without departing from the scope and spirit of the Present Invention. Therefore, it is to be understood that the Present Invention may be practiced other than as specifically described herein. The scope of the present invention as disclosed and claimed should, therefore, be determined with reference to the knowledge of one skilled in the art and in light of the disclosures presented above. 

1. A sandal comprising: a sole, the sole made of an elastic material that decreases in elasticity with wear; and a foot attachment means, the foot attachment means securing the sandal to a wearer's foot while permitting full mobility of each toe of the wearer relative to the foot attachment means.
 2. The sandal of claim 1, wherein the sole comprises a mid-sole and an outer sole, the mid-sole disposed between the outer sole and the foot attachment means, and the mid-sole comprising material that decreases in elasticity and resilience over time.
 3. The sandal of claim 1, wherein the sole comprises a mid-sole and a top sole, the top sole disposed between the mid-sole and the foot attachment means, and the mid-sole comprising material that decreases in elasticity and resilience over time.
 4. The sandal of claim 3, wherein the sole further comprises an outer sole, the mid-sole disposed between the outer sole and the top sole.
 5. The sandal of claim 1, wherein the sole presents a top surface and a bottom surface, and the top surface and the bottom surface are co-planar within the range of from zero degrees to 5 degrees of co-planarity.
 6. The sandal of claim 1, wherein the sole presents a top surface and a bottom surface, and the top surface and the bottom surface are co-planar within the range of from zero degrees to 20 degrees of co-planarity.
 7. The sandal of claim 1, wherein the sole comprises a mid-sole presenting a top surface and an outer sole presenting a bottom surface distal from the mid-sole, the mid-sole disposed between the outer sole and the foot attachment means and the top surface distal from the outer sole, wherein the top surface and the bottom surface are co-planar within the range of from zero degrees to 5 degrees of co-planarity, and the mid-sole comprising material that decreases in elasticity over time.
 8. The sandal of claim 1, wherein the sole comprises a mid-sole presenting a top surface and an outer sole presenting a bottom surface distal from the mid-sole, the mid-sole disposed between the outer sole and the foot attachment means and the top surface distal from the outer sole, wherein the top surface and the bottom surface are co-planar within the range of from zero degrees to 20 degrees of co-planarity, and the mid-sole comprising material that decreases in elasticity over time.
 9. The sandal of claim 1, wherein the sole comprises a mid-sole presenting a bottom surface and a top sole presenting a top surface distal from the mid-sole, the top sole disposed between the mid-sole and the foot attachment means and the bottom surface of the mid-sole distal from the top sole, wherein the top surface and the bottom surface are co-planar within the range of from zero degrees to 5 degrees of co-planarity
 10. The sandal of claim 9, wherein the mid-sole comprises material that decreases in elasticity over time.
 11. The sandal of claim 1, wherein the sole comprises a mid-sole presenting a bottom surface and a top sole presenting a top surface distal from the mid-sole, the top sole disposed between the mid-sole and the foot attachment means and the bottom surface of the mid-sole distal from the top sole, wherein the top surface and the bottom surface are co-planar within the range of from zero degrees to 20 degrees of co-planarity.
 12. The sandal of claim 11, wherein the mid-sole comprises material that decreases in elasticity over time.
 13. The sandal of claim 1, the foot attachment means comprising a forefoot strap, the forefoot strap coupled with the sole and adapted to couple the sole to a human foot without constraining any toes of the human foot.
 14. The sandal of claim 13, wherein the sole presents a top surface and a bottom surface, and the top surface and the bottom surface are co-planar within the range of from zero degrees to 20 degrees of co-planarity.
 15. The sandal of claim 1, the foot attachment means comprising an ankle strap assembly, the ankle strap assembly adapted to detachably couple a human foot to the sole.
 16. The sandal of claim 15, wherein the sole presents a top surface and a bottom surface, and the top surface and the bottom surface are co-planar within the range of from zero degrees to 20 degrees of co-planarity.
 17. The sandal of claim 15, the foot attachment means further comprising a forefoot strap, the forefoot strap coupled with the sole and adapted to couple the sole to a human foot without constraining any toes of the human foot.
 18. The sandal of claim 17, wherein the sole presents a top surface and a bottom surface, and the top surface and the bottom surface are co-planar within the range of from zero degrees to 5 degrees of co-planarity.
 19. The sandal of claim 17, wherein the sole presents a top surface and a bottom surface, and the top surface and the bottom surface are co-planar within the range of from zero degrees to 20 degrees of co-planarity.
 20. A method comprising: a. providing two sandals, each sandal having an elastic sole that decreases in elasticity and in resilience with wear; and b. running with the sandals to cause the elastic sole to decrease in elasticity, whereby the feet of the wearer are gradually strengthened to accommodate bare foot running. 